Method of refining sugar solutions



- Man... 24, 1950 A METHOD OF B EFINING SUGAR SOLUTIONS William A. La Lande, Jr., Upper Darby, Pa., as-

signor to Porocel Corporation, Philadelphia, Pa.,acorporation of Delaware No Drawing. Application March 29, 1941, Serial No. 385,858

12 Claims.

The present invention relates to the refining liquors,' by a combination treatment with a chemic al bleaching agent and an adsorbent comprising activated bauxite;

An object of this invention is the substantial decolorization of sugar solutions by means of chemical bleaching agents and the treatment of the decolorized solutions with activated bauxite to remove from the solutions any excess of bleaching agent and products of the bleaching reaction, as well as a substantial proportion of the invert sugar, ash-forming constituents, and other impurities normally present in the sugar solutions. 7

A further object of this invention is the stabilization of the color of chemically-bleached sugar solutions by treatment of the color-unstable solutions with activated bauxite.

A further object of this invention is the prolongation of the life of decolorizing and refining adsorbents such as activated bauxite by pretreatment of the sugar solutions with chemical bleaching agents.

In the sugar refining industry, it is incumbent uponpractically all refiners to process lower purity sugar solutions, such as wash syrups, as well as to process sugar solutions of relatively high purity,.i. e., washed sugar liquors. In so doing, a refining adsorbent such as bauxite is first employed in the treatment of the high purity solutions, and then in the treatment of the low purity solutions. By operating in this sequence, the bauxite used in the treatment of the low purity solutions is already relatively heavily loaded with impurities removed from the high purity solutions first treated, and consequently has lost considerable of its original refining eiiiciency. However, by employing a chemical bleaching treatment prior to the treatment with bauxite, the color load upon the bauxite is markedly reduced, and the refining capacity or life of the bauxite is considerably increased. Thus, by utilizing a combination treatment with -a chemical bleaching agent and activated bauxite, the overall efliciency of the refining process is substantially improved.

It has been proposed heretofore to decolorize v sugar solutions by means of chemical bleaching invert sugar content of the sugar solutions. In

- containing stituents is actually increased, .since in the bleaching reaction certain of the reaction products are non-volatile substances which are soluble in the sugar solution. The content of invert sugar and ash-forming constituents of sugar solutions decolorized solely by chemical bleaching agents must be reduced or eliminated entirelyby vacuum concentration of the solutions, otherwise the subsequent crystallization of the sugar is rendered more difllcult and the yield of finished sugar is lower. Sulfur dioxide, hydrogen peroxide and ozone readily decolorize sugar solutions without leaving in the decolorized solution additional ash-forming constituents, but some of the bleached coloring materials remain in the solutions, which on standing tend to become colored, due probably to a reversal of the decolorizing reaction. Any excess of bleaching agent in the decolorized solutions must be destroyed by the addition of other chemicals. Furthermore, the chemical'bleaching agents may also exert a deleterious action upon the pH of the sugar solutions, which is'reflected, for example, in the increase in invert sugar in subsequent refining operations.

I have found that the disadvantages of the prior art processes may be substantially obviated by a method involving simultaneous treatment with a chemical bleaching agent and an adsorbent, i. e., activated bauxite, or a treatment first with a bleaching agent and subsequently with activated bauxite.

In accordance with my invention, an impure sugar solution such as washed sugar liquor may be agitated with a suitable quantity of finely divided activated bauxite, for example, 5%-25% of through 100 mesh bauxite, with the simultaneous addition of a bleaching agent which may be either a solid, liquid or gas. The treatment may be carried out at temperatures up to about 200 F., and upon completion of the bleaching and refining reaction, the finely divided bauxite adsorbed reaction products, color bodies, ash-forming constituents, and unused bleaching agent may be separated from the refined sugar solution by filtration, centrifuging, or other suitable means. Alternatively, the impure sugar solution may be treated first with a chemical bleaching agent and thereafter contacted with finely divided bauxite. Bleaching agents such as hydrogen peroxide, sulfur dioxide, ozone, and chlorine are well adapted for simultaneous treatment, while alkali metal or alkaline earth metal peroxides, sulfites, hydrogen sulfltes, hy-

some cases the content of ash-forming condrosulfites, hyposulfltes, permanganates, hypochlorites, and hypochlorous acid are preferably employed prior to bringing the sugar solution into contact with the adsorbent. When it is desired to employ a granular adsorbent, such as -30 mesh 4 This mixture was stirred for minutes at 74 F. and then heated to 175 F. and allowed to stand for one hour. The initial bleaching effect of the hypochlorite treatment at low temperature, i. e.,

activated bauxite, the chemical bleaching agent 5 74 F., was partially offset by the heating to the may be added to the impure sugar solution and the ev ed mp rature of 175 F. to oagulate insolution then percolated or filtered through a bed soluble materials, and as a result, the color of of the adsorbent, or the bleaching agent may be the sugar solution darkened. A heavy scum comincorporated in the impure solution substantially prising insoluble calcium phosphate and flo cusimultaneously with the percolation thereof 10 lated impurities was removed from the surface of through the bed of adsorbent. The percolation the treated sugar solution, and the remainder of is perferably carried out at temperatures within the calcium hypochlorite suspension was added, the range of from about 150 F. to about 180 F. and the mixture stirred for about 10 minutes at Activated bauxites which I have found suitable 175 F. The first addition of hypochlorite is for use in accordance with my invention may be 1 preferably made at a temperature between about prepared by heating naturally occurring bauxite 60 F. and 100 F., whereas the second addition at temperatures of from about 500 F. to about is made at 125 F. to 200 F., and preferably at 1600 F., and screening the activated material to 150 F. to 175 F. While I have shown the use the desired mesh size. Bauxites which have been of monocalcium phosphate for the purpose of reheated between about 600" F. and 900 F. and to acting with the metallic ion of the hypochlorite which contain from about 2% to about 10% como pro e a nso le precipitate, I may embined watenare preferred, although bauxites pl y her id l s a ids supplying anions activated by heating at higher temperatures may which form insoluble calcium salts to bring about be employed. a similar result. As a result of the second addi- By employing my combination treatment of tion of hypochlorite, the color imparted to the chemical bleaching agent and adsorbent, the ash Solution y the heating was substantially econtent and the invert sugar content of the sugar moved. Then 0.5 lb. of a filter aid (Hyfio Supersoiution are reduced by the adsorbent, and the 081) was admixed with the treated solution and reaction products formed by the action of the the mixture filtered in a vacuum filter, whereby bleaching agent upon components of the sugar the filter aid and insoluble reaction products solution are also largely removed, thus preventwere removed from the treated sugar solution. ing reappearance of color in the finished sugar. A sample of the treated solution, when tested The action of the bleaching agent decreases the with KI-H2SO4, gave a positive test for 010 ions. color load on the adsorbent and consequently The treated solution, as well as a sample of unrenders it more efficient in removing ash-forming treated washed sugar liquor, was filtered at a constituents and invert sugar from the solution temperature of 165 F., through 10-30 mesh bauxand lengthens its life as a decolorizing medium. ite activated by heating at 700 F., each filter Furthermore, the method of the present invention containing 12 lbs. of the granular bauxite. Analyreduces the amount of ash and invert sugar to ses of the solutions and filtrates are given in the be eliminated in the boiling pans. In some cases following table (dry basis).

Washliguor, Washliquor, Washliquor,hypoi see Per cent sucrose 98.52 99.13 98.42 99.21 $.79 Per cent invert sugar. 0.70 0.41 0.69 0.39 0.50 Per cent ash. 0.20 0.00 0.28 0.07 0.16 Per cent undetennined. 0.52 0. 40 0. 61 0. 33 0.46 c n: 05.3 6.2 6.5 1.1 3.2 ilt {8T0 ielmmllnns 6- -3 1. 39 5% 010 i011 i positive negative negative Per cent increase in sucrose 0. 61 l 0. 1 0. 69 0. 27 Per cent decrease in- Invert sugar 41. 4 l. 4 44. 3 l5. 7 As 15.9 7.7 73.1 38.5 Undetermined 23. 1 1 l7. 2 36. 5 11. 5 Color 90.4 90.5 98.3 95.1

I The sucrose content decreased 1 The undetennined content increased.

it may be found desirable to adjust the pH of the sugar solution prior to or during treatment with a chemical bleaching agent or an adsorbent, by adding to the sugar solution a small amount of an acid or base.

My invention may be further illustrated by the following examples, which, however, are not to be construed as limiting the scope thereof:

(1) 0.316 lb. of Ca(H2PO4)2.HzO was admixed with 0.45 gal. of water, and the resulting solution was added to 25 gallons of Brix washed sugar liquor. The mixture was agitated for about 5 minutes at a temperature of 74 F. Then 0.32 lb. of calcium hypochlorite (chlorinated lime) was dispersed in 0.45 gal. of water, and 0.317 gal. of the resulting suspension was added to the phosphate-sugar From the above data it will be seen that while hypochlorite bleaching reduces the color of the washed sugar liquor to a substantial extent, the percent sucrose is not increased, the invert sugar is not decreased, and the ash content is changed only slightly. Furthermore, the treated liquor contains 010 ions, which must be removed by an additional treatment, and the original invert and ash content are carried to the crystallizing pans. On the other hand, filtration of the hypochloritebleached liquor through granular bauxite further reduces the color of the liquor, and at the same time decreases the ash and invert sugar content while increasing the percent sucrose. Moreover, since the C10 ion test is negative, no additional chemical treatment is necessary to remove solution above mentioned. 75 the excess treating chemical, and less invert and aceassa ash are carried to the vacuum evaporators. By eliminating the additional chemical treatment, a substantial reduction in refining costs is eflected. Finally, a considerably higher yield of very light colored liquor is obtained by the combination treatment, the preliminary hypochlorite bleach reducing substantially the color load on the bauxite, thereby extending the decolorizing life of the adsorbent.

(2) A washed sugar liquor was admixed with 0.3% of 30% hydrogen peroxide (H202) and permitted to stand for 12 hours at a temperature of 75 F. The treated liquor was tested with KI-H2SO4 and found to contain an oxidizing 6 gal. of 60' Brix washed sugar liquor maintained at 165 F., at a rate of 0.71 cubic foot per hour, for a period of about 2 hours, at which time the bleaching or decolorizing action appeared to be complete. Excess ozone was then displaced from .the sugar liquor bypassing a stream of .air through the solution for about 10 minutes. The treated, as well as the untreated liquors were then percolated through filters each containing 1.76 lb. of 10-30 mesh bauxite activated by heating at 800 F. for 20 minutes and cooled prior to use. Equal volumes of filtrates were obtained, equivalent to 2 lbs. of sugar solids per lb. of bauxite. Analyses oi. the liquors and filtrates are agent. The treated, as well as untreated, liquor given in the following table (dry basis).

Wash liquor Wash wuhuqlm" Washliquor, ozone treated, Analysis liquor omne treated bauxite filtered Per cent sucrose.-. 98. 36 99. 1B 98. 28 99. Per cent invert sugar. 0. 59 0. 40 0. 61 0. 38 Per cent ash 0. 31 0. 00 0. 32 0. (7! Per cent undetermined.. 0. 74 0. 36 0. 79 0. Color 60. 5 6. 2 1. 0 0.7 gl! 7. 1 0. 4 6. 0 i5. 9 er cent increase in sucrose 0. 79 1 0. 08 0. 84 Percent decrease in-- Invert sugar 32. 2 i 8. 4 35. 6 Ash 71. 3 I 3. 2 77. 4 51. 3 0. 7 52. 7 89. 8 98. 3 98. 8

1 The sucrose content decreased. f I The invert, ash, and undetermined content increased.

was filtered at a temperature oi 165 F. through 20-60 mesh bauxite activated by heating at 1000" F., using 1 1b. of bauxite per 0.31 gal. of wash liquor. Analyses of the liquors charged to the filters, and of the filtrates, are given in the I01- lowing table (dry basis). 40 the ozone treated liquor been filtered to the same Wash liquor Wash wash liquor Wash liquor H10, treated Analysis liquor ga Hi0! treat bauxite filtered Per cent sucrose 91. 99. 01 07. 99. 21 0. 75 0. 40 0. 79 0. 51 0.34 0.00 0 35 0.085 1. 11 0.41 1. 01 0. 19 60. 4 4. 8 4. 8 l. 2 EH 6. 5 0. 3 6.3 6. 3 10: in filtrate.. positive negative Per cent increase in sucrose.... 1. 21 0. 05 l. 41 Per cent decrease in- Invert sugar 34. 7 l 5. 3 32.0 Asb i- 78.5 2.0 76.0 Undetermined 63. 1 0. 0 82. 9 Color 90. 0 90.6 97. 7

.1 The invert sugar and ash increased.

Again it will be noted that while the prelimi- 60 color as the untreated, bauxite filtered liquor, the

nary treatment with the chemical bleaching agent, i. e., H202, effected a substantial reduc-.

tion in the color of the sugar liquor, the purity of the liquor expressed as percent sucrose, was substantially unchanged, as were the ash and invert sugar contents of the liquor. 0n the other hand, the combination treatment employed in accordance with the present invention not only increased the percent sucrose, and decreased the ash andinvert sugar content, but gave a much lighter colored sugar liquor which required no chemical treatment to remove excess bleaching agent.

(3) Ozonized oxygen, containing 0.0043 lb. 01'

' decantation. The treated, as well as the untreated liquor was filtered at a temperature of F. through 20-60 mesh bauxite activated by heating at 1000 F., using filters each conozone per cubic foot, was bubbled through 0.61 70 taining 10.25 lbs. 01' the adsorbent. Analyses of the liquors charged to the filters. and of the heating the solution whereby color return is filtrates, are given in the following table (dry eflected and treating said solution I with a basis) thermally activated bauxite.

w an w 11 ii i le 88 (11101, 85 Q1101, n 4 Analysis a bauxite xMno. treated, q filtered treated bauxite I filtered Per cent sucrose 96. 75 07. 66 98. 67 97. 70 Per cent invert sugar. 0. 45 0. 34 0.47 0. 88 0. 17 0. l2 0. 24 0. 02 2. 63 l. 88 2. 8 l. 90 81. 5 5. 5 8. 4 5. 9 H 7. s 6.4 s. 4 Y e. e iltrste yield, gallons. 3. 2 5. 1 Per cent increase in sucrose.- O. 91 1 0.08 0. 95 Per cent decrease in- Invert sugar 24. 7 I 4. 4 l5. 5 Ash 29. 4 l 41. 2 88. 2 27. w l 7. 2 27. 7 93. 3 B9. 7 92. 6

l The sucrose decreased. 1 The invert, ash and undetermined content increased.

() A washed sugar liquor was admixed with the volume of a saturated aqueous solution of potassium permanganate containing 0.1% KMDO4, based upon the solids in the wash liquor, and the mixture was heated and maintained at a temperature of 165 F. for 2 hours, at which bauxite.

time the bleaching action of the permanganate appeared to be complete. To the permanganatetreated solution was then added 0.66% of sodium acid sulfite based on the solids content of the treated solution in the'form of a 10% aqueous solution, and the mixture was permitted to stand until the action of the acid sulfite was complete. Samples of the untreated liquor, the permangahate-treated liquor, and the permanganate-acid sulfite treated liquor, were filtered, at a temperature of 165 F., through 20-60 mesh bauxite activated by heating at 1000 F., using filters each containing 11.85 lbs. of bauxite. Analyses of the liquors charged to the filters, and of the filtrates, are given in the following table (dry basis). v

4. The method of treating a solution of washed sugar which comprises treating said solution with a quantity of a hypochlorite sufficient to substantially decolorize said solution and thereafter 3o treating the decolorized solution at an elevated temperature, and so containing returned color, with activated bauxite.

5. The method of treating a solution of washed sugar which comprises treating said solution with .l5 9. quantity of a hypochlorite sufiicient to substantially decolorize said solution and with a reagent from the group consisting of acids and acid salts capable of forming an insoluble salt with the metal ion of the hypochlorite, separating insolu- 40 ble material from said solution and thereafter Wash li uor Wash Wash gggg g Washli r, KMn% Anal is Wash liquor, liquor, treated KMn r- NaHSO; liquor bauxite KMn haunt; NaHSO: treated, filtered treated treated bauxite filtered filtered Per cent sucrose 98. 68 99. 05 H. 99. 11 8.89 99. 31 Per cent invert sugar- 0.48 0. 34 0. 44 0. 39 0.43 0. 36 Per cent ash l9 0. 12 0. 34 0.10 0. 38 0. 06 Per cent undetermined 65 0. 49 0. 91 0. 40 0. 30 0. 27 o r 4.0 27.4 2.5 17.7 2.6 H 6. 4 8. 4 6. 6 6. 4 6.4 lield filtrate, gallons 8. 7 8. 7 3. 7 Per cent increase in sucrose-.. 0. 37 1 0. 38 0. 43 0. 21 0. 63 Per cent decrease invertsugsr N. 2 8. 3 18. 7 l0. 4 25. 0 h 86.8 i 79. 0 47. 4 i 100. 0 68. 4 Undetermined 24. 6 i 40. 0 88. 4 63. 8- 58. 5 Color 91. 3 40. 4 94. 5 61. 5 94. 2

I The sucrose content decreased. I The ash and invert content increased.

From the foregoing it will be seen that the treating said solution at an elevated temperature,

present invention provides a method oi refining sugar solutionsmore efiiciently than heretofore by the employment of a chemical bleaching agent and an adsorbent. By such method not only is the chemical bleaching treatment simplified but the useful life of the adsorbent is substantially prolonged.

What I claim is:

, 1. The method of treating a sugar solution that has been decolorized with active chlorine, which comprises contacting the solution at an elevated temperature and so containing returned color with a thermally activated bauxite.

2. The method of treating a solution of sugar decolorized with active chlorine which comprises and so containing returned color, with activated bauxite.

6. The method of treating a solution of washed sugar which comprises treating said solution with calcium hypochlorite and monocalcium phosphate in amounts sufllcient to substantially decolorize said solution, separating insoluble material from said solution, and thereafterv treataccess tion and with a reagent from the group consisting of acids and acid salts capable of forming an insoluble salt with the metal ion of said hypochlorite, separating insoluble material from said solution, and thereafter treating said solution at an elevated temperature, and so containing returned color, with activated bauxite.

8. The method of refining a sugar solution which comprises treating said solution with a quantity of an alkaline earth metal hypochlorite sumcient to substantially decolorize said solution and with a reagent from the group consisting of acids and acid salts capable of forming an insoluble salt with the metal ion of said hypochiorite, separating insoluble material from said solution, and thereafter treating said solution at a temperature between 150 F. and 175 F., and so containing returned color, with activated bauxite.

9. The method of refining a sugar solution which comprises treating said solution with a quantity of an alkaline earth metal hypochlorite suillcient to substantially decolorize said solution and with a reagent from the group consisting of acids and acid salts capable of forming an insoluble salt with the metal ion of said hypochiorite, separating insoluble material from said solution, and thereafter treating said solution at an elevated temperature with an additional quantity of said hypochlorite to effect further decolorization and with activated bauxite to prevent color return.

10. The method of refining a sugar solution.-

which comprises treating said solution with active chlorine sumcient to substantially decolorize said quantity of said active chlorine to effect furtherdecolorization-and with activated bauxite to prevent color return.

12. The method of refining a sugar solution which comprises treating said solution with active chlorine to substantially decolorize said solution, and thereafter treating said solution at a temperature between F. and F with an additional quantity of said active chlorine to efiect further decolorization and with activated bauxite to prevent the color return.

' WILLIAM A. LA LANDE, Ja.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 1 Date 1,989,156 Sanchez Jan. 29, 1985 2,059,110 Ioannu Oct. 27, 1930 2,211,727 La Lande Aug. 13, 1940 2,216,758 Sanchez Oct. 8, 1940 

1. THE METHOD OF TREATING A SUGAR SOLUTION THAT HAS BEEN DECOLORIZED WITH ACTIVE CHLORINE, WHICH COMPRISES CONTACTING THE SOLUTION AT AN ELEVATED TEMPERATURE AND SO CONTAINING RETURNED COLOR WITH A THERMALLY ACTIVATED BAUXITE. 